The disclosure relates to a device for determining an estimate of the logarithm of an input variable. The device has an approximation unit which is designed to use an approximation to determine from the input variable a first variable that corresponds to the integer component of the logarithmic value of the input variable. The approximation unit is further designed to determine a second variable which corresponds to an estimate of a non-integer component of the logarithmic value of the input variable. The device further comprises a determination unit for determining a correcting quantity by using the second variable; and an assessment unit for assessing the estimate of the logarithm of the input variable by combining the first variable with the second variable and the correcting quantity.
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1. A device for determining an estimate of a logarithmic value of an input variable, the device comprising: an approximation unit configured to (i) determine a first variable that corresponds to an estimate of an integer component of the logarithmic value of the input variable and (ii) determine a second variable that corresponds to an estimate of a non-integer component of the logarithmic value of the input variable; a determination unit configured to determine a first correcting quantity based on the second variable, wherein the determination unit is configured to determine at least one second correcting quantity that is dependent on the second variable and the assessment unit is configured to assess the estimate of the logarithmic value of the input variable by combining the first variable with the second variable and at least one of the first correcting quantity and the at least one the second correcting quantity; and an assessment unit configured to assess the estimate of the logarithmic value of the input variable by combining the first variable with the second variable and the first correcting quantity.
A device calculates an estimate of the logarithm of a number. It includes an approximation unit that determines two values. The first value represents the integer portion of the logarithm estimate. The second value represents the non-integer portion of the logarithm estimate. A determination unit calculates a first correction value based on the second value. This unit may also calculate at least one second correction value also based on the second value. An assessment unit combines the first value, the second value, and at least one of the first correction value and the at least one second correction value to produce the final logarithm estimate.
2. The device according to claim 1 , wherein the approximation unit is configured to at least one of determine the first variable using a Mitchell approximation, determine the first variable using a base of two, and determine as the second variable a value between zero and one.
In the logarithm estimation device, the approximation unit calculates the integer portion of the logarithm using a Mitchell approximation or using a base of two. The approximation unit also ensures that the non-integer portion of the logarithm estimate falls between zero and one.
3. The device according to claim 1 , wherein the determination unit is configured to determine the at least one second correcting quantity as a combination of a factor that depends on the second variable and at least one of a second constant and a third constant.
In the logarithm estimation device, the determination unit calculates the at least one second correction value by combining a factor dependent on the non-integer portion of the logarithm estimate and at least one of a second constant and a third constant.
4. The device according to claim 1 , wherein the determination unit is configured to determine the at least one second correcting quantity using at least one of a predetermined digit position of the second variable and a predetermined bit of the second variable, the predetermined digit position of the second variable representing the second most significant digit position of the second variable and the predetermined bit of the second variable representing the second most significant bit of the second variable.
In the logarithm estimation device, the determination unit calculates the at least one second correcting quantity using either a specific digit or a specific bit from the non-integer portion of the logarithm estimate. Specifically, the second most significant digit or bit of the non-integer component is used to determine the second correcting quantity.
5. The device according to claim 1 , wherein the determination unit is configured to determine the at least one second correcting quantity as a function of a threshold decision using the second variable.
In the logarithm estimation device, the determination unit calculates the at least one second correcting quantity based on whether the non-integer portion of the logarithm estimate is above or below a threshold value. The calculation uses a function conditioned on this threshold decision.
6. A signal processing device comprising: a read in interface configured to read in a physical variable; a device configured to determine an estimate of a logarithmic value of one of the physical variable and a value derived from the physical variable, the device comprising: an approximation unit configured to (i) determine a first variable that corresponds to an estimate of an integer component of the logarithmic value of the input variable and (ii) determine a second variable that corresponds to an estimate of a non-integer component of the logarithmic value of the input variable; a determination unit configured to determine a first correcting quantity based on the second variable, wherein the determination unit is configured to: determine as the first correcting quantity a first term that is dependent on the second variable in response to the second variable being less than a threshold; and determine as the first correcting quantity a second term that is dependent on the second variable in response to the second variable being greater than the threshold; and an assessment unit configured to assess the estimate of the logarithmic value of the input variable by combining the first variable with the second variable and the first correcting quantity; and at least one of a control unit and a signaling unit configured to provide at least one of a control signal and a data signal using the estimate.
A signal processing device takes a physical measurement as input and calculates an estimate of the logarithm of either the raw measurement or a value derived from it. The device includes an approximation unit that determines two values. The first value represents the integer portion of the logarithm estimate. The second value represents the non-integer portion of the logarithm estimate. A determination unit calculates a first correction value based on the second value. This calculation selects between two terms dependent on the second value, using a threshold comparison: a first term if the second value is less than a threshold and a second term if greater than the threshold. An assessment unit combines the first value, the second value, and the first correction value to produce the final logarithm estimate. Finally, a control unit or signaling unit uses this estimate to generate a control signal or a data signal.
7. A device for determining an estimate of a logarithmic value of an input variable, the device comprising: an approximation unit configured to (i) determine a first variable that corresponds to an estimate of an integer component of the logarithmic value of the input variable and (ii) determine a second variable that corresponds to an estimate of a non-integer component of the logarithmic value of the input variable; a determination unit configured to determine a first correcting quantity based on the second variable, wherein the determination unit is configured to determine the first correcting quantity by using a multiplication of a first constant by a factor that depends on the second variable, the factor being determined by using at least one of a multiplexer and an inverter; and an assessment unit configured to assess the estimate of the logarithmic value of the input variable by combining the first variable with the second variable and the first correcting quantity.
A device calculates an estimate of the logarithm of a number. It includes an approximation unit that determines two values. The first value represents the integer portion of the logarithm estimate. The second value represents the non-integer portion of the logarithm estimate. A determination unit calculates a first correction value. This calculation involves multiplying a constant by a factor that depends on the second value, using either a multiplexer or an inverter to determine this factor. An assessment unit combines the first value, the second value, and the first correction value to produce the final logarithm estimate.
8. A device for determining an estimate of a logarithmic value of an input variable, the device comprising: an approximation unit configured to (i) determine a first variable that corresponds to an estimate of an integer component of the logarithmic value of the input variable and (ii) determine a second variable that corresponds to an estimate of a non-integer component of the logarithmic value of the input variable; a determination unit configured to determine a first correcting quantity based on the second variable, wherein the determination unit is configured to determine the first correcting quantity using at least one of a predetermined digit position of the second variable and a predetermined bit of the second variable, the predetermined digit position of the second variable representing the most significant digit position of the second variable and the predetermined bit of the second variable representing the most significant bit of the second variable; and an assessment unit configured to assess the estimate of the logarithmic value of the input variable by combining the first variable with the second variable and the first correcting quantity.
A device calculates an estimate of the logarithm of a number. It includes an approximation unit that determines two values. The first value represents the integer portion of the logarithm estimate. The second value represents the non-integer portion of the logarithm estimate. A determination unit calculates a first correction value. This calculation uses a specific digit or bit from the second value (non-integer component) to determine the correction value. Specifically, the *most* significant digit or bit is used. An assessment unit combines the first value, the second value, and the first correction value to produce the final logarithm estimate.
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January 14, 2015
March 14, 2017
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